A Green moray eel emerging from a surface of white and blue hard corals and a red soft coral in Palau. PHOTO COURTESY CHUCK SAVALL.

New study helps pinpoint global warming impacts

By Summit Voice

SUMMIT COUNTY — Drilling into coral reef growth bands — much like dendrochronologists study tree rings — enabled Australian researchers to pinpoint impacts of changing sea temperatures, showing that warming oceans have boosted coral growth in some areas — at least in the short-term. In other areas, oceans have already become to warm for optimum coral growth.

The scientists from the Australian Institute of Marine Science cautioned that, despite those findings, rising ocean temperatures and ocean acidification pose serious long-term threats to coral reefs, explaining that their research helps clarify the relative impact of these two threats to date.

To measure those impacts, the researchers extracted cores from massive, long-lived corals from reefs across a 1,000 kilometer north-south gradient in Western Australia to measure annual growth bands, deposited in the calcification process that forms the backbone of tropical coral reef ecosystems.

Changes in growth rates were examined by measuring the annual growth bands; the most reliable method currently available for assessing changes in calcification rates of corals over long time periods.

Focusing in on the most recent 110 years, they were able to compare calcification rates with observed sea temperatures, finding no evidence of a recent widespread decline in coral calcification rates on Australia’s western coral reefs.

Corals at the most northerly sites, where sea temperatures are already high and warming has been small, have shown no change in calcification. In contrast, calcification rates of corals have increased at the most southerly reef sites, where sea temperatures are cooler and warming has been greater.

“This is an important finding, as it helps us better understand the effects of warming waters and rising CO2 levels on coral reefs around Australia and globally,” said Dr. Tim Cooper, a former research scientist with the marine science institute.

“Rapid warming of parts of the tropical oceans, observed to date, appears to be driving coral calcification responses. Some corals in some locations are able to keep up with these changes, whilst others are already showing that the temperature changes have exceeded optimal conditions for coral growth,” he said.

“We are now in an era of rapid environmental change for the world’s coral reefs and this study provides another line of evidence that coral reefs are sensitive to these changes,” said Dr. Janice Lough, the senior principal research scientist at AIMS.

“Coral calcification rates are clearly responding in the short term to temperatures, but in the longer term these responses will be compounded by the progressive impacts of ocean acidification,” she said. “Limiting the magnitude of these rapid environmental changes is fundamental to providing coral reefs, as we know them, with a future.”

The Australian scientists hope to learn more when they finish building an ocean simulator. The giant tanks will give scientists the ability to regulate temperature, acidity, salinity, sedimentation and contaminants in large volumes of water. As a result, critical questions about the impact of our changing environment on coral reefs will be investigated in a controlled but realistic setting.